1. Field of the Invention
The present invention relates to a vibration-damping device for use as an automotive suspension bushing, member mount, body mounting, or the like.
2. Description of the Related Art
As conventional vibration damping device of this kind, there are known suspension bushings such as the one illustrated in FIG. 5 for example, which comprises a metallic outer cylinder member 1 having an outer flange portion 2 at one axial end thereof, a metallic inner cylinder member 3 disposed coaxially within the outer cylinder member 1, with one axial end projecting out from one end of the outer cylinder member 1, a rubber elastic body 4 providing elastic connection between the inner and outer cylinder members 1, 3, and a stopper rubber 5 disposed axially outside the outer flange portion 2. This suspension bushing is mounted onto a component on the vehicle body side, by superposing a washer 6 of annular disk shape onto one end of the inner cylinder member 3 and passing a bolt (not shown) through the bore of the inner cylinder member 3 to thereby attach the outer cylinder member 1 to a suspension arm. By means of this design, clearance is provided between the washer 6 and the stopper rubber 5 so as to avoid excessive deformation of the suspension bushing in the axial direction in response to excessive vibrational input in the axial direction, ensuring stable drivability of the vehicle. However, due to a certain level of variability when installing suspension bushings on vehicles, there tends to be variability in the amount of clearance, creating the problem of difficulty in ensuring stable drivability of a vehicle consistent with settings made on the basis of the design.
This drawback may be solved by the rubber bushing disclosed in JP-A-6-179315, which is shown schematically in FIG. 6. This conventional rubber bushing comprises an inner cylinder member 7 having an outer flange 8 that extends diametrically outward at one axial end, and an outer cylinder member 1 having an outer flange 2 that extends diametrically outward at one axial end. The outer cylinder member 1 is coaxially disposed about the inner cylinder member 7 such that the one axial end of the inner cylinder member 7 projects outwardly from the one end of the outer cylinder member 1 and the outer flanges 2, 8 are situated in opposition in the axial direction, while the inner and outer cylinder members 1, 7 including the outer flanges 2, 8 being elastically connected by a rubber elastic body 9 disposed therebetween.
According to this rubber bushing, the rubber elastic body 9 is interposed between the two outer flanges 2, 8, whereby variability in dimension between the two is avoided, and since the axial length of the rubber elastic body in this area is uniform, stable drivability of the vehicle is ensured. However, the rubber elastic body 9 disposed between the two outer flanges 2, 8 has rigid spring characteristics in the axial direction, and in the case where the thickness of the rubber elastic body 9 between the two outer flanges 2, 8 is less than the thickness of the rubber elastic body 9 disposed between the inner and outer cylinder members 7, 1 in the diametrical direction, the torsion spring characteristics of the rubber elastic body 9 between the two outer flanges 2, 8 may be rigid as well. Thus, the problems of poor vehicle ride comfort, as well as poor durability of the rubber elastic body in the axial direction and the torsion direction may be poor.